Acetic anhydride

Acute Toxicity: inhalation

Administrative data

Endpoint:

acute toxicity: inhalation

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: GLP compliant, near guideline study, available as unpublished report. Minor restrictions in design and/or reporting but otherwise adequate for assessment.

Cross-reference

Reason / purpose for cross-reference:

reference to same study

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

1994

Report date:

1994

Materials and methods

Test guideline

Qualifier:

equivalent or similar to guideline

Guideline:

other: OECD guideline 412

Deviations:

yes

Remarks:

- No clinical pathology, limited pathology (males only)

Principles of method if other than guideline:

Preliminary range findings study in 5 male and 5 time-mated females per group, exposed to vapours of acetic anhydride for 6h/day for 5 days/week for 2 weeks (males) or from days 6-15 post coitum (females).

GLP compliance:

yes

Test type:

other: 2 week repeat dose study

Test material

Test material information

Constituent 1

Reference substance name:

Acetic anhydride

EC Number:

203-564-8

EC Name:

Acetic anhydride

Cas Number:

108-24-7

Molecular formula:

C4H6O3

IUPAC Name:

acetyl acetate

Details on test material:

- Name of test material (as cited in study report): Acetic anhydride
- Physical state: Clear ,colourless, mobile liquid
- Analytical purity: 99.05%
- Purity test date: October 8th 1993
- Lot/batch No.: Not supplied to HRC
- Expiration date of the lot/batch: 8 October 1994
- Stability under test conditions: Adequate for the study
- Storage condition of test material: Dry at 4°C

Test animals

Species:

rat

Strain:

other: Crl:CD BR

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Charles River (UK) Ltd, Manston Road, Margate, Kent
- Age at study initiation: approximately 8 weeks (males), 9-11 weeks (females)
- Housing: 5/cage in suspended cages with stainless steel mesh floors. The cages of each group were housed on a rack in a separate ventilated chamber to avoid cross contamination following exposures
- Diet: SDS Rat and Mouse No. 1 SQC modified maintenance diet ad libitum. Available in home cages.
- Water: Tap water available from polypropylene bottles ad libitum in home cages.
- Acclimation period:12 days (males), 5 days (females)

ENVIRONMENTAL CONDITIONS
- Temperature:18-24°C
- Humidity: 40-70%
- Air changes (per hr): no data
- Photoperiod: 12 hrs dark / 12 hrs light

IN-LIFE DATES: From: 5 January 1994 To: 1 February 1994

Administration / exposure

Route of administration:

inhalation: vapour

Type of inhalation exposure:

whole body

Vehicle:

other: unchanged (no vehicle)

Details on inhalation exposure:

GENERATION OF TEST ATMOSPHERE / CHAMBER DESCRIPTION
- Exposure apparatus: Stainless steel and glass 0.75m3 whole body chambers
- Method of holding animals in test chamber: singly housed in compartmented stainless steel mesh cages.
- Source and rate of air: Compressed, filtered air, air flow rate not reported.
- Method of conditioning air: Chamber air was pre-warmed by passage through a copper coil immersed in a water bath at 60°C.
- Temperature, humidity, pressure in air chamber: 22.5 - 23.2°C , 23-33% humidity (study mean data), internal pressure of 10mm H2O below ambient.
- Air flow rate: approximately 150L/min.
- Air change rate: Not reported
- Treatment of exhaust air: Drawn through an activated charcoal scrubbing system by an extract fan before being vented to atmosphere.

TEST ATMOSPHERE
- Brief description of analytical method used: Gas chromatography.
- Samples taken from breathing zone: yes


Acetic anhydride concentration was determined 6 times during each exposure (approximately hourly intervals), using gas chromatography. Samples were also analysed for acetic acid.
The absence of test substance aerosol was confirmed on one occasion during the study using a Royco Particle Monitor.

Analytical verification of test atmosphere concentrations:

yes

Duration of exposure:

6 h

Concentrations:

0, 24, 103, 407 ppm (males) Analytical
0, 24, 104 ppm (females) Analytical
0, 25, 100, 400 ppm Target

No. of animals per sex per dose:

5

Control animals:

yes

Details on study design:

Rats were exposed to the vapour of acetic anhydride using whole-body inhalation exposure chambers for 6 hours per day.
For males the planned exposure period was 5 days a week (Monday - Friday) for two consecutive weeks. This was only possible at the low exposure level, since, due to treatment-related findings, exposure occurred on only 6 occasions at the intermediate exposure level (100 ppm) and 1 occasion at the high exposure level (400 ppm).
Time-mated female rats were exposed on 10 consecutive days (Days 6 to 15 post coitum inclusive), although restricted to only 7 occasions for females in the intermediate group (100 ppm), again due to treatment-related findings. Due to the adverse effect of exposure at 400 ppm, in males, females allocated to this group were not exposed but retained as concurrent controls.

- Frequency of observations and weighing: Twice daily observations. body weights : Males - week -1, day 1 (pre-exposure) and then daily thereafter. Females - day 1 of pregnancy and then on days 2, 3, 6, 8, 10, 12, 14, 16, 18 & 20 post coitum.
- Necropsy of survivors performed: yes
- Other examinations performed: clinical signs, body weight, food consumption, water consumption, organ weights, histopathology, litter data and foetal examinations

Statistics:

Not appropriate due to small group size.

Results and discussion

Effect levels

Sex:

male

Dose descriptor:

LC100

Effect level:

1 670 mg/m³ air

Exp. duration:

6 h

Remarks on result:

other: 400 ppm (2 died, 3 killed. Clinical signs indicative of respiratory irritation)

Mortality:

400 ppm - 2 males were found dead on day 2 and the other 3 were sacrificed due to their poor clinical condition. Consequently, no females were exposed at this level.

Clinical signs:

other: 400 ppm - During exposure all males showed prone posture, half-closed eyees, lachrymation and exaggerated breathing. After exposure all showed noisy respiration. On day 2, pre-exposure, 2 males were found dead. Of the 3 survivors, all had gasping respi

Body weight:

400 ppm - All animals showed weight loss of approximately 50 g following the first exposure.
100 ppm - Marked bodyweight loss was seen in all animals following the first exposure.
25 ppm - No effects on body weight following the first exposure .

Gross pathology:

400 ppm - All males showed gaseous distension in the gastrointestinal tract, particularly in the stomach. In addition most animals showed brown perinasal staining.
100 ppm - All males and two females had gaseous distension at one or more levels of the gastrointestinal tract. All males had enlarged cervical and/or tracheobronchial lymph nodes and most showed minimal adipose tissue.
25 ppm - All males had enlarged cervical and/or tracheobronchial lymph nodes and two had congestion in the anterior lobe of the right lung.
There were no treatment related macroscopic abnormalities in females.

Other findings:

- Food consumption - At 400 ppm, the group mean cage value was almost zero after the first exposure and at 100 ppm, a marked reductions in food consumption were seen in both sexes following the first exposure. At 25 ppm , group mean food consumption was slightly lower than controls tfollowing the first exposure

- Water consumption - At 400 ppm, the group mean cage value was almost zero after the first exposure and at 100 ppm, marked reductions in water consumption were seen in both sexes following the first exposure. At 25 ppm , group mean water consumption was slightly lower than controls following the first exposure.

Organ weights: At 25 ppm, lung weight was higher and liver and kidney weights were lower in males compared to controls. Organs were not weighed in females.

- Histopathology:
- Potential target organs: Respiratory tract.
- Other observations: HISTOPATHOLOGY: NON-NEOPLASTIC
400ppm - severe degenerative changes were seen in nasal passages, larynx, trachea and tracheal bifurcation and lungs, comprising rhinitis, epithelial ulceration/ degeneration with associated inflammatory exudate and/or epithelial hyperplasia/squamous metaplasia.
100 ppm - severe/slightly less severe degenerative changes were seen in nasal passages, larynx, trachea and tracheal bifurcation and lungs, comprising rhinitis, epithelial ulceration/ degeneration with associated inflammatory exudate and/or epithelial hyperplasia/squamous metaplasia. There was evidence of regenerative hyperplasia and hypertrophy in the lungs. Lymphoid proliferation was seen in macroscopically abnormal lymph nodes.
25 ppm - changes were less severe and comprised rhinitis and hyperplasia in the nasal passages, epithelial hyperplasia and squamous metaplasia in the larynx, slight epithelial hyperplasia in the trachea, epithelial hypertrophy with goblet cells in the lungs and lymphoid proliferation in macroscopically abnormal lymph nodes.

Applicant's summary and conclusion

Conclusions:

Marked acute toxicity, indicative of respiratory irritation, was seen in males at 400 ppm acetic anhydride.

Executive summary:

In a 2 week preliminary toxicity study in rats, marked acute toxic treatment-related effects, indicative of respiratory irritation, were seen in males exposed to 407 ppm acetic anhydride for 6 hours on day 1. On day 2, pre-exposure, 2 males were found dead and the remaining 3 males were killed due to their clinical condition. Females were not exposed to this concentration of acetic anhydride. Clinical signs during exposure included half closed/closed eyes, lachrymation, prone posture and exaggerated respiration. Immediately after exposure all animals showed noisy respiration. Bodyweight loss after exposure was marked with food and water consumption almost zero. Surviving animals showed gasping respiration and two were lethargic and they were therefore killed for humane reasons. Microscopic effects included severe epithelial hyperplasia and/or ulceration in the respiratory tract (nasal paassages, larynx, trachea/tracheal bifurcation and lungs).

At 100 ppm, similar, though less severe clinical signs were seen after the first exposure.

At 25 ppm, half-closed eyes in females was the only clinical abnormality seen during exposure, there were no clinical signs in males and no effects on bodyweight after the first exposure.